Host signal processing modem using a software simulation of a UART

Abstract

A computer system includes a software UART emulation and uses standard operating system protocols to minimized the chance of I/O conflicts between a serial device having a UART and a non-standard serial device which communicates through the UART emulation. A COM driver which can replace a standard COM driver in an operating environment such as provided by Microsoft WINDOWS TM contains the UART emulation. The COM driver can also include a software modem that is accessed through the UART emulation in the same manner as a modem having a hardware UART. The COM driver also sets the device address of the non-standard device on an ISA bus by determining the device addresses of COM port I/O slots used by UARTs, sending a predetermined pattern on the ISA bus to indicate a device address is to come, and then sending a value indicating a device address not used by the UARTs. The pattern has a length sufficient to make inadvertent generation of the pattern unlikely. The non-standard device recognizes the predetermined pattern and selects a device address according to the value from the COM driver.

I claim: 
     
       1. A system comprising: a computer having a processing unit, a main memory, and a local bus;   a device coupled to the local bus, wherein the device occupies an I/O slot that corresponds to a first communications port on the local bus, and the device has a register set with an address assignment in the first communication port that differs from a standard address assignment of a register set for a UART corresponding to the first communication port;   an operating system executed by the processing unit, wherein the operating system includes a procedure for accessing a register set of a UART corresponding to the first communications port; and   a communications driver executed by the processing unit, the communication driver comprising: a UART emulation which in response to an access by the procedure for accessing the register set of a UART, converts the access as required for the register set and address assignment of the device; and   a software modem adapted to convert digital samples from the device to data values transmitted to the UART emulation and adapted to convert data values from the UART emulation to digital samples for the device.     
     
     
       2. The system of claim 1, wherein the software modem performs conversions in accordance with a communication protocol for a communication signal.